This invention relates to a method for manufacturing a heat insulating shaped bar for such use as a heat insulating sash frame, door frame and the like and particularly to a method which uses a shaped bar including a connecting wall (or walls) which forms the top, bottom or intermediate wall connecting a pair of spaced side walls of the shaped bar and has such a shape that any scrap produced during the cutting operation of the connecting wall(s) in the manufacturing of the shaped bar will not remain in a cavity of the shaped bar product.
Processes have been known for manufacturing a heat insulating shaped bar by filling grooves formed in an aluminum sash bar with heat insulating material. One example of such processes is disclosed, for example, in U.S. Pat. No. 4,342,144 and it will be now described referring to FIG. 1 which shows the successive steps in the process in cross section. An aluminum sash bar 1 having an upwardly open groove 2 as shown in FIG. 1(a) is provided, a sheet 3 is placed onto the bottom of the upper groove 2 as shown in FIG. 1(b), and the upper groove 2 is filled with heat insulating material 4 to cover the sheet 3 as shown in FIG. 1(c). Thereafter, the rotary cutting blade 6 of a cutting device is inserted into the lower groove 2' in the sash bar 1 to cut away a portion of connecting wall 5 as shown in Fig. 1(d). The thus obtained intermediate product is turned upsidedown so that the groove 2' is disposed on the top and a sheet 3' is placed onto the open bottom 5 of the now upper groove 2' as shown in FIG. 1(e). Finally, the groove 2' is filled with heat insulating material 4' to cover the sheet 3' in order to obtain a heat insulating aluminum sash bar product as shown in FIG. 1(f).
In the conventional process described hereinabove, however, when the connecting wall 5 is cut by the rotary cutter blade 6 as shown in FIG. 1(d), in fact, the connecting wall 5 is not completely cut away, since the connecting wall 5 is first cut and separated at both side edges of the rotary cutter blade 6, as shown in FIG. 2, which produces a scrap 7 separated from the rest of the wall 5. As shown in FIGS. 3 and 4, the scrap 7 is thrown away from the cutter blade 6 into the cavity of the sash bar 1 where the scrap 7 is left in the form of a web without being subject to further cutting. If the scrap 7 in the form of a web which has a high thermal conductivity remains in the sash bar 1, even after the connecting wall 5 has been cut and the sash bar has been filled with heat insulating material, the obtained aluminum sash bar product will have undesirably poor heat insulating properties. Thus, the conventional process requires an additional step for removing the scrap. In addition, since the produced scrap not only has sharp fins formed at the opposite edges thereof, but is irregularly deformed, the removal of the scrap is troublesome. The generation of the scrap has been one of the problems inherent to the conventional process.
It is, therefore, a primary object of the present invention to provide a method for manufacturing heat insulating shaped bars which can prevent production of scrap in the form of a web during the cutting operation of the connecting wall.
The present invention may be summarized as a method for manufacturing a heat insulating shaped bar including a pair of spaced side walls and a heat insulating connecting portion formed by heat insulating material and connecting the pair of side walls together from an integrally extruded metal shaped bar having the pair of side walls and a connecting wall (or walls) extending and connecting between the side walls; wherein the connecting wall(s) includes on one surface thereof a recess having sloped sides and extending longitudinally of the metal shaped bar and whereby the method includes a step of cutting the material of the connecting wall(s) from the other surface at the area of the recess.
In the method of this invention, since the gap which separates the connecting wall into two wall sections is formed at the thinned recessed portion at first and is then widened toward the thicker sloped side portions, no scrap in the form of a web is left uncut nor remains in the cavity of the shaped bar.
Many other advantages, features and additional objects of the present invention will become apparent to persons skilled in the art upon making reference to the following description and the accompanying drawings which show preferred embodiments of the present invention by way of illustrative example.